Thermal Imaging for Switchgear Hotspot Inspection

Why Switchgear Needs Routine IR Surveys

Loose connections, corroded bus joints, and overheated cable terminations announce themselves as temperature anomalies long before they fail. A thermal imaging survey performed annually catches 80% of incipient switchgear failures, prevents arc-flash events, and is required by most insurance carriers and NETA MTS-2019. The cost of one infrared scan compares favorably to a single uncontrolled outage.

Pre-Inspection Checklist

• Load condition: at least 40% of normal load, 100% preferred
• Steady-state temperature: equipment energized for at least 1 hour
• Ambient temperature: recorded for delta-T calculations
• Wind speed: less than 5 m/s for outdoor switchgear
• PPE: arc-rated to the available short-circuit current at the panel

Survey Technique

1. Open inspection windows or remove covers per safe work permit
2. Image each phase, line and load side, of every disconnect, breaker, and bus joint
3. Capture both visible and infrared image with the same field of view
4. Mark each finding with location, equipment ID, and load current at the moment
5. Re-image suspect spots from a second angle to rule out reflection artifacts

Severity Classification (NETA)

• 0–9 °C above ambient or similar component: monitor next survey
• 10–19 °C: action within 6 months
• 20–39 °C: action within 30 days
• 40+ °C: immediate action, consider de-energizing

Common Findings

• Loose lug on outgoing breaker: hottest phase, others cool
• Failing splice in bus duct: gradient along the duct length
• Failed capacitor in PFC bank: hot can with low current draw
• Overloaded cable: uniform heating along the run, hottest at terminations

Reporting

Each finding requires a thermal image, a visible-light reference image, equipment ID, load condition, severity rating, and recommended action. Document the instrument used (e.g., EK-TI800 series) and the emissivity settings (typically 0.95 for oxidized busbars) to ensure repeatability in next year's survey.